NB Head Rebuild - Advice Please

[Okibi]

As some Natmeet'sters may have noticed my valve stem seals seem like they're on the way out.

With all the down hill driving, especially stuck behind slow moving vehicles it drank a fair bit of oil.

So I was going to just rebuild my old NB head so I can swap it into the car without pulling the engine out. (I don't have access to a hoist these days).

What should I do to avoid this happening again (apart from changing my driving style).

Are they better quality valve stem seals?

I was also thinking I should consider making the engine stronger in case I decide to use the AVO manifolds i've had laying about.

What's would be the logical upgrade steps based on affordability and usefulness.

Porting and polishing?
Better head gasket?
ARP head bolts?
Titanium springs?
Bigger Valves?
Cams?

[Okibi]

Nope, don't want a full rebuild or a t28

[AJ]

if you're gunna do the head Dave, you might as well do it properly & get the whole head rebuilt, porting & polishing is a given as far as i'm concerned........as for cams & bigger valves, how wild do you want to go??.................if you only want mild, i'd suggest sussing out getting your existing cams reground to a nice mild application that'll give you some extra kick in the torque range & either regrind (if they're ok) the valves you have, or just bang new ones in without going oversize, titanium springs??.....only if you're after an 11 sec monster .......i'm sure there are beefed up springs on the market that'll handle an AVO setup without going the expensive route.

ARP head bolts??.......again, is this a justified expense for what you're aiming for??.........i'd just replace the existing head bolts with new standard ones if it were me.

valve stem seals are valve stem seals as far as i know, they either last or they don't, in the old days, engines that saw long stretches of time without a start used to dry their stem seals out, & of course they'd fail after a few restarts, but i never had any problems with any of my garage queens through the '90's, so i spose they improved the product somewhat.

changing driving style won't stop them doing what they do IMO.


there ARE better head gaskets out there, just don't go cheap arse with it, get the best you possibly can, single torque application being the best option.

my 2c.......take it or ignore it, i'm easy

[adamjp]

When I got my head rebuilt and ported/polished the two things I wish I had done were.....

Get the exhaust valves and ports Jet-Hot/HPC coated. This will reduce the heat transfer to the exhaust valve, reducing wear. I didn't do this as I simply couldn't affort it at the time, what with all the other stuff that I was doing. It is about $11 per valve, and $11 per port. Plus shipping.

Get the HLA bosses cut back a tiny bit to fit bigger cams. I just plain forgot to ask for this.

If you can afford it, you may wish to consider bigger valves. I didn't do this as the extra machining would have eaten into my porting budget. Advice from the machinist was that the mild porting would deliver more than the bigger valves.

I agree with the comments on springs and studs. Fairly unecessary on a street dríven car with anything up to mild boost.

[hamish71]

You will find a very good valves/springs etc at: http://www.belfabracing.com/

Next, find somewhere to do headwork for you. At a very minimum, get a multi-angle(5) valve job. next look at port matching, and then, if you want, get a full race port. Whole lot will set you back about $2500. If you have money to burn you can get a competition port, whereby they port, then flow, then port, then flow, until the optimum is found. Parts and standard rebuild are more like $600-800, with valve job and porting stepping up from there.

[NMX516]

There are variable quality valve stem seals... I don't know if it's such an issue with the 5, but when I rebuilt the head on my other car, the consensus was to go with genuine Nissan only, as the aftermarket ones available didn't tend to last very well... 40,000kms was an average max it seemed.

In summary, worth doing some research into the valve stem seals as to which ones are the best.

[Mr Morlock]

Okibi I think NMX516 is probably right. Like many things you buy there is no ready way of assessing the quality. Oil stem seals are probably not conversation pieces though the OEM products must comply with Mazda specs and suppliers have Quality systems which should deliver consistently good product.I reckon the Mazda product might be the way to go. .

[Matty]

My advice is: be realistic. And be conservative.

You can throw heaps of money at working on a head, but unless you throw a whole heap more on other stuff, it's a waste, and at best you'll end up with a racey motor that will be gutless at the bottom.

The NB heads flow quite well. And most (non-racecar) head shops who would do a cheap port job will probably make it flow worse if anything. A cleanup of any casting dags is as much as you will probably need.

Cutting back the lifter bores to be able to fit bigger cams is only useful if you fit bigger cams (>9mm lift). Which will need new valve springs... And an ECU... And a set of shim-under-bucket lifters... Are you really going to do all of that?

Personally I would have a look at the ports, remove any obvious casting dags, make sure the ports match the inlet manifold, give it a shave for a slight compression bump (again, be realistic - too much will retard the cam timing), slap it back in and forget about it.

But if you want to go further, Dodgy Steve stuck a Mazdaspeed intake cam in his NB motor with some cam gears for some apparently good results (Megasquirted). This was based on Randy Solomiata's setup.

Grab a copy of Modern Engine Tuning by A G Bell for good reading.

[Okibi]

I don't want to increase compression.

Matty, as usual you're spot on. I was thinking about using some of my polishing practise for performance gains instead of bling and cleaning some casting. I don't think i'll bother polishing the exhaust side.

I'd love to know if there's any better valve stem seals but so far I haven't found anything.

I would consider a better head gasket and perhaps ARP head studs to help if I turbo down the track.

I don't think i'll bother with cams/cam gears yet.

I won't bother with bigger valves yet either.

I love to rev the engine so I was wondering if better valve springs would be worth the cost.

Here's what FM do to their heads

Where's a good place to get gaskets etc from ?
Here's FMs link

[Matty]

I'll check the book tonight about valve seal recommendations - I think it has something about ideal clearances. But whether you can correlate that to any particular brand etc is unknown... you're at the mercy of the head builder. Might be able to custom ream something though.

I wouldn't worry about valve springs unless you're going to increase the rev limit, and increase the valve lift.

As for port cleaning, you don't want a shiny finish. Slightly rough is better apparently, it gives a turbulent boundary layer and better flow.

Knowing how these engines can handle reasonable boost input in stock form, I continue my 'don't bother' opinion on things like studs and special head gaskets.

[CT]

SE valve stem seals if your going OEM but I reckon ACL or normal stock ones will be fine. I take it your head wasn't done with the rest of the donk? Do as Matty suggests, a general clean up and leave it at that. If you start stuffing around, sily things will start to happen. ie, fancy head gaskets are a minimum of 4 times the cost of OEM ones. So far, the NB ones from Mazda are the best from what I've seen.

[irwin83r]

im actually in the process of gathering bits to do a similar thing myself..

got a set of tomie pon cams and a haltec E8 to go in so am doing all the little bits of maintenance i can think of while of got so many parts of the car appart and exposed...

i'm looking at pulling my intake manifold apart totally and cleaning it as well as what you have mentioned about removing and cast dags and aligning the ports.

i'd like to shave the head as i can do it at work free but doopersprints wont allow it in 2b last time i checked anyway how much people normally shave off an nat asp street/track 5 anyway? what kinda comp ration bump dose it achieve??

Edit:
cars coming upto 160,000ks too so its a tad over due for afew things aswell. will be doing timing belt, tensioners and seals aswell as a new radiator and coolant flush as the current one is starting to go that scary colour...
what else should i look at (sorry for hijack ) i hear with hard driving around 160,000 is about when valve springs start to go.. what about the valves them selves and valve stem seals? should i do them all?

[Okibi]

One site I looked at last night had the same part numbers for the 99NB valve stem seals as for a Toyota 2JZ.

Can anyone else confirm they're the same part?

I might have more aftermarket options if I look at Toyota parts.